As mentioned earlier, technically, magnetic pickups are small magnets with fine wire coils. These small magnets produce a magnetic field around them. When the metal strings of the guitar are strung by the user, a vibrating motion is generated inside this magnetic field which changes the magnetic flux of the field. According to the law of electromagnetism, this change in the magnetic flux produces an electric charge in the wire coil around the magnet.
Usually, the magnetic pickup arrangement consists of six small individual magnets whose distance from the metal string can be arranged using a knob. This means that lesser the distance from the metal string, stronger will be the signal.
It is to note that each of these metal strings is made to vibrate at a particular rate. The amount of electrical charge produced by the vibrating motion in the pickup coils is then sent to an electric circuit, consisting of resistors and capacitors, which controls the tone and amplitude of the electric signal. The electric signal is then sent to an amplifier which is electrically connected to the magnetic pickups.
An amplifier makes this electric signal audible through the loud speakers. Unlike conventional amplifiers, electric guitar amplifiers are not only used to produce loud and clear sound but also for little distortion, which is a much needed feature for producing desirable music.
Most of the modern electric guitars are provided with several tones and volume controlling circuits which helps in controlling the string vibration and thus the electrical charge produced. These adjustments are mainly done with the help of knobs provided on the neck of the guitar. Thus, the more the number of electrical circuits, the better the guitar can be adjusted for different sounds.